Blackberry

I was in Racine Wisconsin visiting my sister this last week. We went to the Habitat For Humanity Restore facility and I was asking the gentleman there if he had any sewing machines. He said he did if I wanted to fix it up. I said can I see it and he showed me a 301A. He said he was getting ready to trash it but when he found out I was interested he sold it to me for $10. I have been tinkering with it and I don't think there is too much wrong with it. It doesn't have a bobbin case and it appears there is quite a bit of threads or debris of some kind behind the part that holds the case. Now my question is, can this part be taken off or how do I get in the back of it to get this stuff out. You can see by the picture there is a thread dangling also.